Microsoft has joined forces with development platform vendor Xamarin to make it easier for Windows developers to create cross-platform apps for smartphones, tablets and PCs.

The partnership was announced at the launch of Visual Studio 2013, which took place at an event in New York on Wednesday.

The most important part of the partnership is a technical collaboration to better integrate Xamarin’s technology with Microsoft’s developer tools and services, including Visual Studio 2013. The goal is to make it easier for C# developers to share code when building native apps for iOS, Android, Mac OS and Windows.

Xamarin has implemented APIs for both iOS and Android, so anything that can be done in Objective-C or Java can be done in C# using its tools, according to the company.

“We have done the C# thing for a while, but always on our own. So for us its significant that we are collaborating with Microsoft and are being endorsed as a platform for developing cross-platform apps,” said Nat Friedman , CEO and co-founder of Xamarin.

Microsoft has a big megaphone and developers still listen to the company, which means people who have never tried Xamarin’s tool or maybe not even heard of the company will now learn about what it can do to help them, Friedman said.

As a first step to make it easier to share code, Microsoft will release reference assemblies for its portable class library, which lets developers write a single DLL that can run on multiple platforms, with very broad licenses that allow it to be used anywhere.

Friedman isn’t alone in thinking that the partnership is a big step for Xamarin.

“This is huge for Xamarin, which has been doing pretty well already capitalizing on the raw talent in the Microsoft developer ecosystem for other platforms. But it’s also smart for Microsoft to shift its thinking in that it is likely to attract developers to its ecosystem as they can leverage their efforts for Windows platforms,” said IDC’s program director for software development research, Al Hilwa, via email.

Mobile developers are still struggling to justify multi-platform development costs and typically end up doing the top one or two platforms only, according to Hilwa.

The collaboration also aims to help Microsoft developers learn more about how to write mobile apps. MSDN subscribers will get free access to the recently launched Xamarin University.

The first class will teach developers that already use Visual Studio and know C# all the fundamentals needed to architect iOS and Android apps, including how to build user interfaces, integrate with Web services and write location-based features, according to Friedman.

MSDN subscribers will also get access to a 90-day free Xamarin trial, and a discount if they want to buy. Since its inception two years ago, Xamarin has attracted over 430,000 developers in 70 countries, including more than 20,000 paying accounts, it said.

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